Measured Noise Temperature Research Articles

Road traffic noise correction coefficients associated with temperature. Case study and comparison with calculation methods

Strategic noise maps by means of calculation methods allow the administrations managing road infrastructures to estimate the level of noise generated during their operating regime. The sound power emitted by this source of noise depends on multiple factors, which can be classified into three groups: meteorological conditions, variables associated with the physical characteristics of the road and variables related to road traffic. This study evaluates how temperature can have an effect on the sound pressure level generated in the surroundings of the infrastructure. A case study is presented in this paper where on-site measurements of noise levels and temperature were performed next to a two-lane national road with mixed traffic under regular operating conditions. The results were compared with the scientific literature and those coefficients proposed in CNOSSOS-EU calculation method for temperature correction.

Over-the-Air Noise Temperature Measurement

Noise temperature is one of the key performances of RF components, such as the amplifiers in those receivers and transmitters. It is essential to measure the noise temperature accurately; however, the traditional conduction method is no longer suitable for those components with integrated antennas, e.g., antennas in packages (AiP) or antenna on chip (AoC). This paper proposes a solution for noise temperature measurement based on the over-the-air (OTA) method. First, the concept and the problem of noise temperature for those devices integrated with RF components and radiation elements are reviewed, the proposed OTA noise temperature measurement and calibration methods are presented, the measurement systems are set up and at both C band and millimeter-wave band with different measurement distances under both transmitting and receiving states are demonstrated in detail, and the measured results are compared and discussed which verifies that this proposed method is technically feasible for the OTA noise temperatures with high accuracy.

Evaluation of Noise Level in Selected Primary Schools in Ikorodu Division Area of Lagos State, South-Western, Nigeria

Noise pollution is a significant issue of concern other than air and water pollution since it harms physical, psychological and social wellbeing. This research work is to evaluate the noise (dB) levels in twelve primary schools selected using stratified random sampling from six Local Council Development Area (LCDA) within Ikorodu Division of Lagos State. Noise level, humidity and temperature measurements were carried out at three points within the school premises of selected schools at time intervals of 8 am to 9 am, 10 am to 11 am and 12 noon to 1 pm using a factory-calibrated Digital Sound Level Meter AS844+. The data collected were subjected to statistical analysis both descriptive and inferential. The results obtained revealed that the average noise levels are 71.54 dB between 8 am and 9 am, 73.65 dB between 10 am and 11 am and 71.75 dB between 12 noon and 1 pm. Average humidity ranges from 66.45% and 61.01% while average temperature ranges from 31.09 0C to 33.19 0C. These noise levels were significantly above the World Health Organization’s recommended school noise levels of 35 dB for classrooms and 55 dB for playgrounds. This study creates awareness on the level of noise in primary schools and also promotes a simple method for regular assessment of the noise levels in these environments towards encouraging an action plan on the part of Government.

THE INFLUENCE OF MISMATCHES ON THE RESULTS OF MEASURING THE NOISE TEMPERATURE AND THE EFFECTIVE APERTURE OF ANTENNAS BY RADIO ASTRONOMY METHODS

The radio astronomy methods for measuring antenna properties allow to measure noise temperature and effective antennas aperture with high accuracy when the antenna and the standard load are ideally matched in the input of the radiometer. Due to appear-ance of high-efficiency antennas, the requirements to high-precision measurements of noise temperature and the effective aperture of antennas have increased. The earth meth-ods for measuring those antenna parameters turns out to be insufficient and, in some cas-es, impossible. In practice, antenna parameters measuring and radioastronomy research with high efficiency convincingly proved that the difficulties in measuring by earth meth-ods are relatively easy to overcome. As high efficiency antennas and low noise receivers have appeared the require-ments to measuring antenna properties with high accuracy have increased. For measuring the parameters of large antennas more than 10 cosmic standard sources are chosen. Among them standard sources Cassiopeia - A, Cygnus - A, Taurus - A, and Virgo – A meet the requirements, that have an aperture of up to 80 m of mirrors. In real systems antenna – radiometer, standard load – radiometer always exist a whole reason leading to power re-reflection. At that, the measure and values are characterized by errors (mismatch errors). The goal of the work is consideration of errors which are conditioned by mismatch and giving methods to decrease them, which allows to eliminate the influence of mis-matches in the measurement results. The influence of mismatch are studied when we measure noise temperature and effective antenna aperture in a system which consists of a noisy signal source plus radiometer. Methods which decrease and fully eliminate the influ-ence of those mismatches in measurement results are proposed.

Low Noise Amplifier With 7-K Noise at 1.4 GHz and 25 °C

This article describes a low noise amplifier which is believed will have a transformative impact because of the following characteristics: 1) the noise temperature at a physical temperature of 25 °C is a factor of 4 lower than typical commercial LNAs; 2) the noise decreases to 4.5 K at a temperature of -40 °C, a temperature realizable with solid-state coolers; 3) the LNA has an integrated, extremely stable noise source to facilitate measurement of system noise temperature; and 4) the amplifier is powered by a dc voltage and controlled by a tone signal on the RF output cable thus requiring no additional wiring. The amplifier benefits systems in the low microwave frequency range with low background temperature, such as those for space communications and radio astronomy, but without the capital and maintenance costs of cryogenic systems. This article describes the construction and test results with an emphasis on the manufacturability and accuracy of the noise measurements. Finally, the noise of a system deploying the LNA is described.

Noise Temperature Measurements for Axion Haloscope Experiments at IBS/CAPP

The axion was first introduced as a consequence of the Peccei-Quinn mechanism to solve the CP problem in strong interactions of particle physics and is a well motivated cold dark matter candidate. This particle is expected to interact extremely weakly with matter and its mass is expected to lie in $\mu$eV range with the corresponding frequency roughly in GHz range. In 1983 P. Sikivie proposed a detection scheme, so called axion haloscope, where axions resonantly convert to photons in a tunable microwave cavity permeated by a strong magnetic field. A major source of the experimental noise is attributed to added noise by RF amplifiers, and thus precise understandings of amplifiers' noise is of importance. We present the measurements of noise temperatures of various low noise amplifiers broadly used for axion dark matter searches.

Demonstration of a wideband submillimeter-wave low-noise receiver with 4–21 GHz IF output digitized by a high-speed 32 GSps ADC

We report on a 275–500 GHz heterodyne receiver system in combination with a wideband intermediate-frequency (IF) backend to realize 17 GHz instantaneous bandwidth. The receiver frontend implements a heterodyne mixer module that integrates a superconductor-insulator-superconductor (SIS) mixer chip and a cryogenic low-noise preamplifier. The SIS mixer is developed based on high-current-density junction technologies to achieve a wideband radio frequency (RF) and IF bandwidth. The IF backend comprises an IF chain divided into two channels for 4.0–11.5 GHz and 11.3–21.0 GHz and an analog-to-digital converter (ADC) module that is capable of high-speed sampling at 32 Giga samples per second with 12.5 GHz bandwidth per channel and an effective number of bits of 6.5. The IF backend allows us to simultaneously cover the full 4–21 GHz IF range of the receiver frontend. The measured noise temperature of the receiver frontend was below three times the quantum noise (hf/kB) over the entire RF band. A dual-polarization sideband-separating receiver based on this technique could provide up to 64 GHz of instantaneous bandwidth, which demonstrates the possibility of future wideband radio astronomical observations with advanced submillimeter-wave heterodyne receivers.

Analysis and Research on the Centimeter Band Receiver Amplitude Calibration Method

The receiver is a signal receiving device in a radio telescope system. As an important parameter to characterize the receiver performance, noise temperature is very practical to calibrate accurately. The traditional receiver noise temperature calibration method is the cold and ambient load method. Through the establishment of K-band ambient receiver, and its amplitude calibration test platform of the cold and ambient load method, chopper wheel method, and ambient and hot load method, comparison and analysis of the above three methods were carried out. The test and calculation results show that the test accuracy of the cold and ambient load method is about 1.3%, that of the chopper wheel method (nonlow elevation) is about 3%, and that of the ambient and hot load method is about 9%. The test accuracy of the ambient and hot load method is slightly lower than that of the above two methods. The analysis is mainly due to the uncertainty of the hot load temperature and the small temperature difference between the two loads, which leads to the deterioration of the overall accuracy. But the advantage is that the method can perform real-time calibration in the process of observation, and it is easier to implement than the traditional cold and ambient load method. The results of noise temperature measurement are compared with those of theoretical calculation, the error is basically within 10%, and it can satisfy the demand of the noise temperature test. In the future, we expect that on the basis of increasing the hot load temperature, further experiments were carried out on the thermostatic treatment of hot load and the accuracy of temperature acquisition, and finally we hope that this method can better meet the testing requirements of receiver noise temperature and radio source amplitude calibration.

340 GHz Double-Sideband Mixer Based on Antenna-Coupled High-Temperature Superconducting Josephson Junction

Wireless communication and sensing are moving from microwave, millimeter-wave into the terahertz (THz) frequency regime to meet the fast growing demand of ultrahigh data-rate communications and super resolution imaging. Faced with severe atmospheric absorption attenuation and the lack of power efficient transmitting source at the higher band, ultrasensitive and cost-effective receiver frontend technology is required for advanced THz wireless systems. To date, the most sensitive heterodyne mixers, the key components of frontend receiver systems, are based on low-temperature superconducting materials that operate at liquid helium (4.2 K) temperature range, requiring expensive and bulky cryogenic cooling systems thus hindering them from commercial applications such as wireless communications and sensing. In this article, we present a 340 GHz double-sideband fundamental mixer based on thin-film antenna-coupled high-temperature superconducting (HTS) Josephson junction that operates at a much higher temperature range attainable with smaller and cheaper cryocoolers. Based on our innovative work in terms of advanced device circuit and on-chip antenna designs, accurate parametric simulation analyses, and Josephson junction parameter optimizations, the reported mixer exhibits a measured noise temperature of 470 and 780 K at operating temperatures of 20 and 40 K respectively at 340 GHz, a performance significantly higher than any HTS THz mixers reported to date.

Noise Temperature Measurement System of Normal and High Temperature Load Method

Microwave receiver is a special equipment used to receive radio signals in radio telescope. The noise temperature of receiver is an important target to test sensitivity. The lower the noise temperature is, the higher the sensitivity is. Therefore, the measurement of noise temperature is very important. The classical cold and ambient load method can measure noise temperature well, but it can not be carried out during observation. In addition, the performance of microwave devices is not unchanged, and noise temperature will vary with the ambient temperature and test equipment, so real-time measurement of noise temperature is important. We set up a noise temperature measurement system based on normal and high temperature load method. Through this system, noise temperature can be calculated by measuring the radiation power and temperature of blackbody at normal temperature and after heating to 150°C. Compared with results of the cold and ambient load method, the maximum test error is 12.3% in five tests, and the other test errors are less than 10%. The results can confirm that the normal and high temperature load method could be hopeful to satisfy the normal test requirements of centimeter-band normal temperature receiver.

275–500-GHz Wideband Waveguide SIS Mixers

We have successfully demonstrated low-noise and wideband SIS mixers for the 275–500-GHz radio-frequency (RF) band, aiming to cover Atacama Large Millimeter/submillimeter Array band 7 (275–373 GHz) and band 8 (385–500 GHz) simultaneously. The waveguide SIS mixers integrate a multisection impedance transformer with a parallel-connected-twin-junction or single-junction circuits based on Nb/AlN/Nb trilayers with a critical current density of 31 kA/cm2. In order to achieve the targeted broadband performance, we designed an asymmetric one-side waveguide probe placed across a reduced height waveguide with dimensions 100 μm × 580 μm. The shape of the waveguide probe was optimized to have nearly constant impedance at around 35 Ω in the desired RF range. For evaluation of the receiver performance, we have established a dual-band noise temperature measurement system. The system implements a broadband corrugated horn antenna and a 15-dB RF/local oscillator (LO) waveguide coupler based on WR-2.3 (290 μm × 580 μm) waveguide size. The target bandwidth is too wide for typical LO sources at these high frequencies, and, therefore, we applied a dual-band LO injection system utilizing two different LO sources and an LO diplexer. The IF chain uses a cryogenic isolator and a low-noise amplifier with a typical noise temperature of 2.1 K over the 4–8-GHz range. The measured double sideband receiver noise temperature is two to three times the quantum noise at all LO frequencies for both the twin-junction and the single-junction circuits.

Measurements of Noise Temperatures of Radio Telescope Receiver System of a Two-Element Radio Interferometer with Very Long Baseline

The results of experimental investigations of the noise temperatures of the RT-13 radio telescope receiver system of a two-element radio interferometer with a very long baseline in the 2.2–2.6, 7.0–9.5, and 28–34 GHz frequency range are presented. The measurements were taken by wide-aperture low-temperature noise generators developed and certified on the standard baseline of VNIIFTRI. The error of measuring the noise temperatures of the radio telescope receiver system was determined. The confidence limits of the measurement error (for fiducial probability P = 0.95) were not more than 3.7 K.

Sensitivity and Resolution of a Heterodyne Receiver Based on the NbN HEB Mixer with a Quantum-Cascade Laser as a Local Oscillator

We present the results of experimental studies of the basic characteristics and operation features of a terahertz heterodyne detector based on the superconducting NbN HEB mixer and a quantum cascade laser as a local oscillator operating at a frequency of 2.02 THz. The measured noise temperature of such a mixer amounted to 1500 K. The spectral resolution of the detector is determined by the width of the local-oscillator spectral line whose measured value does not exceed 1 MHz. The quantum-cascade laser could be linearly tuned with respect to frequency with the coefficient 7.2 MHz/mA within the limits of the current oscillation bandwidth.

On the Possibility of Breaking the Heterodyne Detection Quantum Noise Limit With Cross-Correlation

The cross-correlation sensitivity of two identical balanced photodiode heterodyne receivers is characterized. Both balanced photodiodes receive the same weak signal split up equally, a situation equivalent to an astronomical spatial interferometer. A common local oscillator (LO) is also split up equally and its phase difference between both receivers is stabilized. We show by semi-classical photon deletion theory that the post-detection laser shot noise contributions on both receivers must be completely uncorrelated in this case of passing three power splitters. We measured the auto- and cross-correlation outputs as a function of weak signal power (system noise temperature measurement), and obtain a cross-correlation system noise temperature up to 20 times lower than for the auto-correlation system noise temperature of each receiver separately. This is supported by Allan plot measurements showing cross-correlation standard deviations 30 times lower than in auto-correlation. Careful calibration of the source power shows that the auto-correlation (regular) noise temperature of the single balanced receivers is already very near to the quantum limit as expected, which suggests a cross-correlation system noise temperature below the quantum limit. If validated further, this experimentally clear finding will not only be relevant for astronomical instrumentation but also for other fields like telecommunications and medical imaging.

Specific Capacitance Dependence on the Specific Resistance in Nb/Al–AlOx/Nb Tunnel Junctions

The junction specific capacitance (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ) is an essential parameter in designing tuning circuitry for superconductor- insulator-superconductor (SIS) mixers. However, our knowledge of the junction capacitance only relies on the few available empirically obtained C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> versus specific normal resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> A) relations, which are inconsistent especially at low R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> A values, R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> A <; 40 Ω·μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . In this paper, we report the Nb/Al-AlO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> /Nb SIS junction capacitance data from our recently presented direct microwave (4 GHz) measurements at 4 K for junctions with various R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> A values ranging from 8.8 to 68 Ω·μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . New insight is provided into the extraction of the true geometrical specific capacitance of SIS junctions. We show that even at such low microwave frequencies, the so-far-neglected nonlinear susceptance is significant, especially for junctions with low R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> A values. This susceptance originates from the real part of the response function, I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">KK</sub> , which can be calculated through the Kramers-Kronig transform of the dc tunnel current. The new specific capacitance, which accounts for this contribution, is presented as a function of R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> A. We provide an improved and more accurate C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> A) relation, which can be a reliable and useful tool for circuit designers. The obtained C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> A) relation is compared with those available in the literature, and the possible reasons giving rise to the disparity among these relations are discussed. By comparing the modeled and the measured noise temperature of the APEX SHeFI band 3\(385-500 GHz) double sideband mixer, we show that the new C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> A) relation offers a great potential for improving the performance of SIS mixers.

Dependence of noise temperature on physical temperature for cryogenic low-noise amplifiers

We present the results of noise-temperature measurements for four radio astronomy MMIC low-noise amplifiers (LNAs) at physical temperatures from 2 to 160 K. We observe and confirm recent reports that the noise temperature of an LNA exhibits a quadratic dependence with respect to the physical temperature. We are also able to confirm the prediction by Pospieszalski that below a certain physical temperature there is no further significant reduction in noise temperature. We then discuss these results in the context of both the Pospieszalski noise model and some recent Monte-Carlo simulations, which have implied that at very low temperatures, heating of the electron channel above ambient temperature may help to explain the behavior of the drain temperature parameter.

The 700–950 GHz Superconducting Receiving Structures for Radio Astronomy

We have designed, fabricated, and tested the waveguide receiving element, which is based on the tunnel superconductor–insulator–superconductor structures, for the frequency range 790–950 GHz. Two Nb/AlN/NbN tunnel junctions are incorporated in a microstrip line consisting of the bottom NbTiN-film electrode with a thickness of about 300 nm and the top 500 nm-thick aluminum electrode. The production-process optimization allows one to ensure the following characteristics of these junctions: submicron area (0.5 μm2 for each junction), current density about 30 kA/cm2, and band gap width 3.2 mV. Such tunnel junctions ensure the receiver operation in a wide frequency range (700–950 GHz), which was confirmed by the Fourier transform spectroscopy and the noise-temperature measurements. At a frequency of 725 Hz, the corrected noise temperature of the receiver amounts to 120 K, which is only threefold greater than the quantum limit hf/kB, where h is the Planck’s constant, f is the frequency, and kB is Boltzmann’s constant. In the upper part of this frequency range, the noise temperature increases up to 390 K.

High-Gap Nb-AlN-NbN SIS Junctions for Frequency Band 790–950 GHz

We have designed, fabricated, and tested superconductor-insulator-superconductor (SIS) mixers based on Nb/AlN/NbN twin tunnel junctions for waveguide receivers operating in a frequency range of 790-950 GHz. Electromagnetic simulations and measurement results of the mixer performance are presented. The junctions have a high gap voltage of 3.15 mV and a high current density of about 30 kA/cm 2 , providing a wide receiver band, which was confirmed by Fourier transform spectrometer (FTS) and noise temperature measurements. The corrected receiver noise temperature varies from 240 K at low frequencies to 550 K at the high end of the band. The influence of the SIS junction heating on its characteristics has been studied and compared to another similar high current density technologies. The heating does not have a critical impact on the mixer performance.

The Measurement and Analysis of System Noise Temperatures of the TM65m Radio Telescope at Low Frequency Bands1,2

At first, the receiving system of the Tianma 65m radio telescope (TM65m in brief) and its noise characteristics at the L, S, C, and X four frequency bands are described. Then, a few measuring methods of system noise temperature are discussed, and the major factors affecting the noise temperature measurement are analyzed, including the errors caused by the non-linearity, feed network insertion loss, mismatch, and so on. With the Y-factor method the noise temperature of the noise source calibrated in the laboratory is verified, indicating that its accuracy attains ∼0.2K. Finally, the system noise temperatures actually measured at the four frequency bands and an analysis on the result are given.

Active cold load MMICs for Ka‐, V‐, and W‐bands

Three active cold load circuits operating at millimetre-wave frequencies are presented. The circuits have been manufactured using 100 nm metamorphic high electron mobility transistor technology. On-wafer measurements of noise temperature and match are presented. Measured noise temperatures are 75 K, 141 K, and 170 K at 31.4 GHz, 52 GHz, and 89 GHz, respectively. Measured reflection coefficients are better than −19 dB for all designs.